1. 30 Jul, 2020 2 commits
    • Marc Zyngier's avatar
    • David Brazdil's avatar
      KVM: arm64: Ensure that all nVHE hyp code is in .hyp.text · bdbc0c7a
      David Brazdil authored
      Some compilers may put a subset of generated functions into '.text.*'
      ELF sections and the linker may leverage this division to optimize ELF
      layout. Unfortunately, the recently introduced HYPCOPY command assumes
      that all executable code (with the exception of specialized sections
      such as '.hyp.idmap.text') is in the '.text' section. If this
      assumption is broken, code in '.text.*' will be merged into kernel
      proper '.text' instead of the '.hyp.text' that is mapped in EL2.
      
      To ensure that this cannot happen, insert an OBJDUMP assertion into
      HYPCOPY. The command dumps a list of ELF sections in the input object
      file and greps for '.text.'. If found, compilation fails. Tested with
      both binutils' and LLVM's objdump (the output format is different).
      
      GCC offers '-fno-reorder-functions' to disable this behaviour. Select
      the flag if it is available. From inspection of GCC source (latest
      Git in July 2020), this flag does force all code into '.text'.
      By default, GCC uses profile data, heuristics and attributes to select
      a subsection.
      
      LLVM/Clang currently does not have a similar optimization pass. It can
      place static constructors into '.text.startup' and it's optimizer can
      be provided with profile data to reorder hot/cold functions. Neither
      of these is applicable to nVHE hyp code. If this changes in the future,
      the OBJDUMP assertion should alert users to the problem.
      Signed-off-by: default avatarDavid Brazdil <dbrazdil@google.com>
      Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
      Link: https://lore.kernel.org/r/20200730132519.48787-1-dbrazdil@google.com
      bdbc0c7a
  2. 28 Jul, 2020 7 commits
  3. 07 Jul, 2020 19 commits
  4. 05 Jul, 2020 12 commits